Agricultural soil legacy influences multitrophic interactions between crops, their pathogens, and pollinators

Soil legacy influences plant interactions with antagonists and below-ground mutualists. Plant-antagonist interactions can jeopardize, while soil mutualists can enhance, plant-pollinator interactions. This suggests that soil legacy, either directly or mediated through plant symbionts, affects pollinators. However, despite the importance of pollinators to natural and managed ecosystems, there is almost no information on how soil legacy affects plant-pollinator interactions. We assessed effects of soil management legacy (organic vs. conventional) on floral rewards and plant interactions with wild pollinators, herbivores, beneficial fungi, and pathogens. We used an observational dataset and structural equation models to evaluate hypothesized relationships between soil and pollinators, then tested observed correlations in a manipulative experiment. Organic legacy increased mycorrhizal fungal colonization and improved resistance to powdery mildew, which promoted pollinator visitation. Further, soil legacy and powdery mildew independently and interactively impacted plant traits important to pollinators, including floral traits and floral reward nutrients. Our results indicate that pollination could be an overlooked consequence of soil legacy and suggests opportunity to develop long-term soil management plans that benefit pollinators and pollination.